make a column matrix with outputs of a for loop

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fatima hd
fatima hd 2015-7-20
回答： David Schubert 2015-7-20
I have a for loop and I want the outputs of each iteration to sit in a column matrix. for example i have the code below:
for i=1:5
a=[1 2; i 3]
[P,Q]=eig(a);
end
for the first iteration Q(i=1)=[0.2679 0; 0 3.731], for second iteration I have Q(i=2)=[-0.2361 0; 0 4.2361] and so on. I want to construct a 10*1 column matrix in which all the outputs are after each other like this:
S=[0.2679 3.731 -0.2361 4.2361 ....]
but I really don't know how. it would be appreciated if u help me.
  1 个评论
Mathieu
Mathieu 2015-7-20
编辑：Mathieu 2015-7-20
So you want to concatenate some vectors? Because if yes:
b = [];
for i=1:1:5
a = [1 2]
b = [b a];
end
And the result is a vector with [1 2 1 2 1 2 1 2 1 2] (5 times the vector a)

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采纳的回答

David Schubert
David Schubert 2015-7-20
Use diag(Q) to obtain only the eigenvalues on the diagonal of Q, and then concatenate:
mat = [];
for i=1:5
a=[1 2; i 3];
[P,Q]=eig(a);
mat = [mat; diag(Q)];
end

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